1. Field
The following description relates to a passive Radio Frequency IDentification (RFID) system, and more particularly to data modulation/demodulation for high-speed data transmission from a reader to a tag.
2. Description of the Related Art
In general, Radio Frequency IDentification (RFID) is a technology that reads out or records information using wireless frequencies in a contactless manner from tags having unique identification information in order to identify, track and manage products, animals, or people attached with tags. An RFID system consists of a plurality of electronic tags or transponders (hereinafter referred to as ‘tags’) having unique identification information and attached to products and animals, and an RFID reader (hereinafter referred to a ‘reader’ or an ‘interrogator’) for reading and writing information.
A passive RFID system is a system in which a tag having information of an object does not have an apparatus for power and wireless signal transmission. The passive RFID system is enabled to provide information of each object and may be applied in more fields and industries compared to barcodes. RFID is used in a variety of applications to recognize an individual unit only using a tag ID. Recently, in the aircraft, automobile, shipbuilding, and steel industries, a technology for high-speed reading/writing large data using tag user memory greater than 32 Kbyte or 64 Kbyte is required for management and maintenance of components. However, the conventional passive RFID technology is not enough to implement the above task, and thus, it is necessary to develop a technology that allows high-speed transmission and receipt of data through communication between readers and tags.
A reader in the passive RFID system transmits data to a tag by using Pulse-Interval Encoding (PIE) defined in ISO/IEC 18000-63. However, the maximum data transmission rate of PIE is merely 128 Kbps which is not suitable for high-speed transmission and receipt of large data. For example, if a user wants to write large data in a tag with a reader, the reader needs to include data to be stored in a tag memory and an address thereof in a write command of the reader. In this case, if data to be written is large, it is necessary to divide the data and transmit a write command to a tag repeatedly. For this reason, a technology of transmitting data from a reader to a tag at high speed is required. In addition, if a user reads large data from a tag using a reader command of a reader, an error rate of a received data packet may increase, and thus, it is necessary to divide the data and transmit a read command to the tag repeatedly. Even in this case, a technology of transmitting data from the reader to the tag at high speed is required. In addition, given the fact that a tag operates passively, encoding data transmitted from a reader should have a simple structure.